Background

I first noticed this and raised the issue here KSP-CKAN/CKAN#2733, but it looks like a bug with mono so I decided to make this issue.

Steps to Reproduce

1. Run mailclient with mono --arch=32 mailclient.exe in Terminal
2. Select any textbox
3. Write with Japanese input in the textbox

mailclient.zip

https://github.com/mono/mono/blob/master/mcs/class/System.Windows.Forms/samples/mailclient.cs

Current Behavior

No text is added to the textbox. A small window with the beginning of the Japanese input show up at the bottom of the screen. Application becoming unresponsive for a few seconds and then a message "Developer Tools Access needs to take control of another process for debugging to continue" appears. After I click cancel several times the application crash and I get an apple bug report message.

Expected Behavior

Japanese text appearing in the text-box

On which platforms did you notice this

[X] macOS 10.14.4 (18E226)
[ ] Linux
[ ] Windows

Version Used:

Mono JIT compiler version 5.16.0.220 (2018-06/bb3ae37d71a Fri Nov 16 17:12:11 EST 2018)
Copyright (C) 2002-2014 Novell, Inc, Xamarin Inc and Contributors. www.mono-project.com
TLS: normal
SIGSEGV: altstack
Notification: kqueue
Architecture: amd64
Disabled: none
Misc: softdebug
Interpreter: yes
LLVM: yes(3.6.0svn-mono-release_60/0b3cb8ac12c)
GC: sgen (concurrent by default)

Stacktrace

I don't know how to do this, but here is the terminal output:
TerminalOutput.txt